Noob motor holder troubles

Ok. I mounted the 6 inch tire back into the upper slot and you can see how much I had to tighten the wheel to get most of the slack out of the belt.Even with a little slack left in the belt I am already hitting in a few places with the tire.

The picture below shows the first spot which is easily fixed with some light shaving.But the real problem is that I am wedged against this outer bottom bolt and outer side piece of the motor holder. Plus....Plus the upper bolt and motor tab as well.When i mount the tire itself in a position that it is not hitting anything you can see i have way to much slack in the belt!
This is a reference picture to the size of the gear that is on my motors. Do I need a smaller belt? A bigger gear on my motors? Maybe both?
The item number on my belt says HTD-405-3M-12